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business models, strategies and technologies

Superseding shipbuilding symmetry?

Finnish-built “oblique” icebreaker with an asymmetrical hull gets more done – and breaks the mould for ship design

With most kinds of seriously gnarly machinery and equipment, development usually consists of upticks in easy appreciable commercial metrics like size, capacity or speed. Incremental, marginal improvements but rarely anything seriously radical.

In ships, for example, the basics of hull shape haven’t really changed since prehistoric times – long, narrow, symmetrical and designed to sail straight ahead, albeit with a plethora of shapes to help them do so with evolving and varying degrees of efficiency. (OK, there’s the whole multi-hull/SWATH thing, but they, too, are fundamentally long, narrow and symmetrical, as well as basically designed for sailing straight ahead).

Shipping channels feeling the squeeze

When the sea freezes over, traditional icebreakers use their weight, size and power to crush and bulldoze crusts of ice up to 3 metres thick. The icebreaker then leaves a narrow, open channel corresponding to its own waterline beam, through which other vessels can follow.

But there have been dramatic increases in Arctic ship traffic in recent years, and both cargo vessels and crude oil carriers have got steadily bigger. This means it now often requires two icebreakers – plus an increasing number of other expensive and expensive-to-run support vessels – to open a channel wide enough for these ships to pass through. This in turn makes icebreaking costs skyrocket, in addition to being a major hindrance to plans for opening up Russia’s strategic Northern Sea Route, as well as keeping other Arctic shipping routes passable and safe. In 2010, only three or four ships sailed the Northern Sea Route, but in 2012 the number had risen to forty-three. The majority of the ships using this route carry liquefied natural gas (LNG) or crude oil to East Asian markets, raising concerns about risks of environmental damage as well as search and rescue issues in this inaccessible and sparsely populated area.

Oblique movement widens the channel

Arctech Helsinki Shipyard Inc. – a relatively recent joint venture between STX Finland Oy and Russian United Shipbuilding Corporation (USC),  starting operations on the awesomely inauspicious date of 1 April 2011 – reckons it’s found a fairly radical way to tackle all these challenges in one fell swoop, by dropping the whole idea of symmetrical hulls, as well as junking the time-honoured design parameter dictating that ships normally sail in the direction they’re pointing.

Lots of ships have non-symmetrical superstructures and operating equipment, and some have different lumps and bumps on the hull for special purposes. But the basic shape of ship hulls is still basically the same as in the days of dug-out canoes – more or less symmetrical. The Oblique Icebreaker NB 508 changes all that.

Breaking ice sideways

Breaking ice sideways

Arctech Helsinki Shipyard Inc. specialises in Arctic shipbuilding technology, the yard making proud claims to have delivered about 60% of the icebreakers in operation around the world. In spring 2014, Arctech delivered the remarkable Baltika icebreaking multipurpose emergency and rescue vessel to the Russian Ministry of Transport. The Oblique Icebreaker NB 508 design features an asymmetrical hull whose heavily reinforced port (left, for landlubbers) side slopes steeply to make icebreaking more efficient.

This means that – in addition to tackling ice packs head-on in the conventional way – NB 508 is able to move obliquely through the ice at  angles of up to 30 degrees, providing the game-changer capability of forging a channel that’s up to twice as wide as the vessel’s own hull.

Sideways achieves more

Sideways achieves more

This is made possible by an advanced-technology propulsion system consisting of three rotating Azipod® azimuth thrusters that turn through 360 degrees. These are placed asymmetrically below the ship’s hull, with two propulsion units at the back and one at the front. These diesel-electric thrusters enable the vessel to move just as efficiently ahead, astern and obliquely, and with a high degree of manoeuvrability.

The use of Azipod® thrusters – and the Rolls-Royce Mermaid azimuth thrusters competing in the same market – is beginning to big make differences to the capabilities and manoeuvrability of many different types of otherwise conventional ships, but Arctech has taken the technical opportunities a big step further by rethinking what can be achieved – by introducing a breakthrough asymmetric hull design.

Non-symmetrical = double duty

The unique – and sufficiently so to be patented, apparently – asymmetric hull design also brings other money-saving operating advantages. In conventional thinking, icebreakers only do one job – the one they’re designed for. Ironically, in times of global warming this means many countries’ expensive icebreakers tend to sit in harbour all year round, with crews twiddling their seafaring thumbs and soaking up public funds to no avail.

The NB 508 hull design means the vessel can do much more than “merely” keeping iced-up shipping lines clear. In addition to its rescue capabilities, the vessel also provides environmental clean-up capabilities, which are disproportionately important in the pristine Arctic marine environment.

While the steeply sloping port side of the hull is reinforced for icebreaking, the near-vertical starboard side is designed to help clean up any spills of oil or other petroleum products, using an advanced oil recovery system. The vertical side of the hull gets used as a sweep, and when the vessel moves obliquely through an oil slick, the oily water is rapidly and effectively guided through a hatch in the hull into a special skimmer tank that separates the oil from the water.

Forget conventional thinking

Ships don’t have to follow the long, narrow and symmetrical pattern that logs bestowed upon our prehistoric forefathers, and they no longer have to be designed around sailing in the direction their bow is pointed.

But the big challenge lies in being actually able to rethink the basic parameters for hull design rather than the practicalities of shipbuilding. The thought has to be there before the engineering can implement it.

External info
http://arctech.fi/ships/nb-508/ http://texags.com/forums/16/topics/2605149 https://www.youtube.com/watch?v=zwe0MHRaqhA